Drug delivery devices are in widespread use. For example, they can be applied by persons who do not have a formal medical background. Medical devices can be used to administer accurate and predefined doses of a medical product such as heparin or insulin. In particular, such devices can be used for a healthcare therapy whenever there is demand for a medical or pharmaceutical product being administered on a regular or an irregular basis over a short term or a long term period.
These circumstances set a number of requirements for the drug delivery device of this kind which should be met. The device should be robust in construction, yet easy to use in terms of the manipulations of the parts, easily to be understood by the operator concerning the handling, and/or be suitable for an accurate delivery of the required dose of the medical or pharmaceutical product. Dose setting should be easy and unambiguous. In cases when the device is to be disposable rather than reusable, the device should be cheap to manufacture and easy to dispose of.